An electrical insulator of the above-indicated type is designed in particular to serve as an insulating support member for an outdoors high-voltage installation, as described in U.S. Pat. No. 4802731.
That document discloses a first disposition in which the optical waveguide is installed along a linear or even helical path in the inside volume of the support element which is constituted by a laminated tube. Unfortunately, the inside volume of the tube is, in general, filled with a pressurized dielectric gas, such as SF.sub.6, so as to prevent electrical arcs from striking between the high-potential end of the insulator and the low-potential end of the insulator. As a result, that disposition for the optical waveguide involves gastightness problems because the optical waveguide must pass from the inside volume of the tube to the outside of the tube.
The above-mentioned document also discloses a disposition in which the optical waveguide is embedded in the thickness of the laminated tube. Actually, it is proposed to combine filament winding as performed in manufacturing the laminated tube with winding the optical waveguide. In practice, such a method is very difficult to implement, in particular because the optical waveguide is subjected both to mechanical stresses and to thermal stresses when the tube is heated after the filament winding step. Furthermore, it is difficult to hold one end of the optical waveguide while it is being wound, and to control the go-and-return winding of the filament while simultaneously controlling winding of the optical waveguide. In addition, the ends of the tube have to be cut off, which is difficult when the optical waveguide is present.
The above-mentioned document also proposes to embed the optical waveguide in the elastomer material that covers the laminated tube and that constitutes the insulating fins. But such a method is also very difficult to implement when the fins of the insulator are constituted by a continuous strip of elastomer material that is obtained by extrusion and that is helically wound around the tube. Moreover, that method requires the pitch at which the optical waveguide is wound around the tube to be identical to the pitch at which the extruded continuous strip constituting the fins is wound. It is necessary to be able to vary the length of the waveguide between the two ends of the tube independently from the number of fins in order to adapt the acceptable voltage gradient that is established in the optical waveguide.